Hidden Anchors

Quickie shut offs

I ran into a fuel dock and another boat with my speedboat in my younger years. I was coming in fine. if not a little fast, tried reverse it would not go into gear. I killed ignition but the momentum kept me going. I learned a good lesson. Good thing everyone on other boat was so drunk they didn't care I tore rub rail off boat.

On mechanical diesels, shutting off fuel is not a good way to turn off engine. You will get air in fuel lines and then you have to prime everything. Therefore you shut air off to intake. This turns engine off. Also it could take several minutes to turn off if all you do is cut fuel.

 

I agree with what mydauphin has said about diesel killing. It's not like a gas engine where you can short the plugs and kill it all instantly. The sure-fire way with diesels is a simple flap on a cable, that when closed completely seals the intake. I'd fit such a thing for sure, costs almost nothing and a big safety bonus.
I still don't see how a wonky autopilot could run a boat up on the rocks like that, unless the crew weren't keeping watch properly. Autopilot doesn't respond to commands? Yank out its power cord, or if the control head's down below, send a crewman into the engine room to pull the cord out of its terminals. Can always fix the cord later, but the hull's another story...

 

I think all this is proving my point that they are not suitable for safe navigation. The fact that they can and do fail with catastrophic results is enough for me.

I drove a little Azimut with twin Cats in it once with electronic engine controls. Ok it was nice and responsive and so smooth. But when docking it was allways in the back of you mind that you may not have controll.

If I had been on a long trip I think I would find myself moving the throttles now and again just to assure myself that they were still working. Especially when arriving at the destination.

I have no answer why aircraft do not have a problem exept that aircraft stuff is of much higher quality to the point that cost doesnt matter.

Marine stuff is crap at as much as they can sell it for ,---but that another thread.

Electric controls are to get over the problems that cables have,--which to be honest is due to bad fitting. A morse system fitted correctly can be smooth and very responsive.Neutral is neutral and full is full, with complete confidence. ( even without power)

My boat has a bridge and two engines,--I made my own cable splitters for the bridge to handle 2 engines. (Will post picture if any one interested)

 

Theres a bit of confusion here on fuel shut offs. There is electric diesels that have electronically controlled injectors. There is dieslels with an electric fuel cut off switch in the pump which is how you stop them ( like a car) and there is the old system that has nothing,--give it fuel and it will run forever.

Stopping a diesel by cutting off the air would mean fuel still being pumped into the cylinder. The cylinders would be in negative pressure as it was gasping for air,--(valves still working) and this would draw up oil from the the lower cylinder walls. Ok not a problem but what a black smokey mess when you fire it up again.

Your turbo will not appreciate such abuse and you may pull in water from the water cooled exhaust as the exhaust valve opens at BDC after power stroke (which there was not one) and there is only a depresion

 

I don't think of an intake-cutoff valve as being the main shutoff system. I tend to think of it as a backup, that is guaranteed to kill the whole system in the event that all else fails.

 

When I repower my boat, we decided to used the venerable detroit diesel 6-71 none-turbo inlines. I got the pair from a Tug they had just been rebuild and the price was right. Their starters are compressed air and their throttle also used air. So did shutoff of air flap. I got these because I expect to cruise in South America and other remote locations and wanted something easy fix to and get parts for.

The compress air is not a problem on my boat since I have several sources available. The air starters are extremely simple, reliable and have ridiculous torque to start motors. Motors have zero electronics, as a matter of fact even the gauges are mechanical. Presently I am in process of installing electronic senders so I can have gauges on bridge.

These engines can even operate underwater, just need air and fuel. One time the air shut off broke and I could not turned one of then off. With the fuel in system it kept running and running. Finally turned it off by stuffing the exhaust.

Anyway, I hooked up Hynautic hydralic controls and they work great. I would have gone with cables but the lengths where kind of long. The electronics where cheaper, but I go scared ater boat ran dock in Ft. lauderdale from throttle servo failure.

I presently have what looks like a choke cable to emergency shut offs, but I have to jump from bridge down. Some big boats have a hydraulic brakes on shafts for real emergencies.

I dont know any other way to turn off these guys, they want to keep running.

 

The main reason for installing intake-air shut-offs is in case of a fire, though I can see that for last-resot engine stops it would work eventually too.

 

Whats wrong with pulling the engine stop on the pump? Or loosening the injector pipes?

Decompression mechanism pehaps?